1. Field of the Invention
The present invention relates to a metal powder structure and a method of fabricating the same, and more particularly, to a nanostructured metal powder comprising a plurality of nano-grains and a method of fabricating the same.
2. Description of the Related Art
The interest in nanometer-sized (nano-) particles or clusters is due to their unique and improved properties. Nano-particles have enormous potential in metal and ceramic processing. For example, nano-particles can be sintered at much lower temperature (<0.5 Tm; Tm=melting temperature). In addition, the mechanical, electronic, optical, magnetic and thermal properties of nano-crystalline materials are different from those exhibited by their conventional counterparts. Their unique physical and chemical properties have created considerable enthusiasm for nanotechnology development.
U.S. Pat. No. 4,610,718 discloses a method for manufacturing ultra-fine particles. In the conventional method, arcs are struck across an electrode and a metal material serving as another electrode, thereby vaporizing the metal material into ultra-fine particles (also referred to as metal nano-powders with average diameter about 1˜100 nm). Nevertheless, the metal nano-powders are very active due to their relatively large surface area. Employing the metal nano-powders in battery application, for example, could be very dangerous, sometimes could even result in explosion, since the unstable metal nano-powders would cause violently chemical reaction with oxygen or electrolytes. In addition, the much greater surface area of the metal nano-powders causes poor fluidity and dispersion for electrode slurries.
In order to solve the above problems, a passivation treatment can be performed on the surface of the metal nano-powders. For example, the surface of the metal nano-powders may be coated with an organic thin film. However, this method not only seriously decreases the mass transfer rate and electrical conductivity of the metal nano-powders but increases manufacturing costs.
Another method for solving the above problems is employing granulation (or particle making) process to obtain larger particles (μm-scaled particle). However, the conventional granulation method suffers from problems such as difficultly in controlling particle morphology, internal void defects, and hollowness issues. These seriously affect material and thus device performances. Also, the process increases manufacturing costs as well.
Thus, considering the performance, safety and convenient utilization, a novel metal powder structure and a method of fabricating the same are brought out in the present invention.